This invention relates to a unit and more particularly to a gas spring unit. Gas spring units are frequently used e.g. in motor-vehicle constructions for facilitating the movement of a movable part, such as a trunk lid or an engine hood between a closed position and an open position
Moreover, it is possible to use such gas spring units for facilitating the movement of a movable roof element of a motor-vehicle construction with respect to the basic framework of such a motor-vehicle construction. More particularly, gas spring units as considered by the present invention may be used for facilitating the movement of a roof element, such as a foldable roof element with a cabriolet. In such a cabriolet, it may occur that the roof element is loaded by gravity forces towards an opening position within a first range of movement adjacent said opening position and that the roof element is also load by gravity forces towards a closing position within a second range of movement. In a third range of movement between said first range of movement and said second range of movement, the gravity forces may be compensated for by guiding forces so that no substantial gravity forces act onto the foldable roof element towards the opening or the closing position. In such a situation, it may be desirable to use a spring device for facilitating the movement of the foldable roof element between the opening position and the closing position. When using such a spring device for facilitating said movement, specific characteristics are desirable for the spring device. Such, the spring device should support the movement of the foldable roof element through the first range of movement away from the closing position. On the other hand, it is not desirable at all that the foldable roof element is accelerated by gravity forces when being moved through the second range of movement, i.e. when approaching the closing position.